title: A colorimetric assay for determination of methyl parathion using recombinant methyl parathion hydrolase.
abstract: A simple, rapid and sensitive colorimetric dipstick assay for the detection of the organophosphorous insecticide methyl parathion (MPT) residue in vegetables was developed. The assay was based on the hydrolysis of MPT by a recombinant methyl parathion hydrolase (recMPH), the encoding gene of which was isolated from Burkholderia cepacia, a soil bacterium indigenous to Thailand. This reaction generates protons leading to a change in pH that correlates with the amount of MPH present. Hence, the pH indicator bromothymol blue was used to monitor the MPH hydrolysis as the associated color changes can be observed by the naked eye. The recMPH was immobilized on a PVDF membrane to establish a dipstick assay format. The assays could detect MPT residues in spiked vegetable samples at the concentration of 1 mg/L without using analytical instrumentation. The test is reusable and stable for up to 3 months in the absence of any preservatives.
authors.affiliation: Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, Bangkok, Thailand.
authors.forename: Dau Hung
authors.initials: DH
authors.lastname: Anh
authors.forename: Kritsananporn
authors.initials: K
authors.lastname: Cheunrungsikul
authors.forename: Jesdawan
authors.initials: J
authors.lastname: Wichitwechkarn
authors.forename: Werasak
authors.initials: W
authors.lastname: Surareungchai
mesh_terms: D003124:Colorimetry / Q000379:methods*; D006867:Hydrolases / Q000378:metabolism*; D007306:Insecticides / Q000032:analysis / Q000378:metabolism; D008743:Methyl Parathion / Q000032:analysis* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism*
chemical_list: D007306:Insecticides; D011994:Recombinant Proteins; D008743:Methyl Parathion; D006867:Hydrolases